This is the two coin Collector's Set in 90% Silver. with the Ultra Rare Kennedy Matte Half. Authorized mintage was 500,000 but in fact only 62,000 were sold making this by far and away the lowest mintage Kennedy Half! Many of these sets were broken up to fill holes in Kennedy Half albums. so who knows how many of these sets remain?
https://www.youtube.com/watch?v=U8DEw5iJD8A&t=19s